Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
Incoloy 800H Socket Head Cap Screws
Socket head cap screws (DIN 912 / ISO 4762) are cylindrical-head Allen-drive fasteners machined from Incoloy 800H ASTM B408 round bar for high-temperature service to 815 deg C (1500 deg F) in restricted-clearance assemblies where a hex-head wrench cannot fit. The cylindrical head carries a hex socket drive (Allen key) and the shank is fully threaded with controlled head-underside fillet. TorqBolt machines socket head cap screws in diameter range M3 to M48, with shank lengths cut to print. Across-flats of the hex socket follow the DIN 912 schedule (2.5 mm hex on M3 through 24 mm hex on M48). Socket head cap screws are the low-clearance alternative to hex cap screws on petrochemical instrument enclosures, heat-exchanger end-cover bolting and high-temperature pump assemblies. Every socket cap ships with EN 10204 type 3.1 mill test certificate documenting heat number, ASTM B408 chemistry, solution-anneal cycle and ASTM grain size 5 verification, with type 3.2 third-party witness on call-out.
Socket Head Cap Screw Dimensions (DIN 912 / ISO 4762)
| Size designation | Across flats / OD | Head / nut height | Thread pitch | Standard reference |
|---|---|---|---|---|
| M3 | 3.0 mm OD | Head OD 5.5 mm; Hex socket 2.5 mm | 0.5 mm | DIN 912 / ISO 4762 |
| M4 | 4.0 mm OD | Head OD 7.0 mm; Hex socket 3.0 mm | 0.7 mm | DIN 912 / ISO 4762 |
| M5 | 5.0 mm OD | Head OD 8.5 mm; Hex socket 4.0 mm | 0.8 mm | DIN 912 / ISO 4762 |
| M6 | 6.0 mm OD | Head OD 10 mm; Hex socket 5.0 mm | 1.0 mm | DIN 912 / ISO 4762 |
| M8 | 8.0 mm OD | Head OD 13 mm; Hex socket 6.0 mm | 1.25 mm | DIN 912 / ISO 4762 |
| M10 | 10.0 mm OD | Head OD 16 mm; Hex socket 8.0 mm | 1.5 mm | DIN 912 / ISO 4762 |
| M12 | 12.0 mm OD | Head OD 18 mm; Hex socket 10 mm | 1.75 mm | DIN 912 / ISO 4762 |
| M16 | 16.0 mm OD | Head OD 24 mm; Hex socket 14 mm | 2.0 mm | DIN 912 / ISO 4762 |
| M20 | 20.0 mm OD | Head OD 30 mm; Hex socket 17 mm | 2.5 mm | DIN 912 / ISO 4762 |
| M24 | 24.0 mm OD | Head OD 36 mm; Hex socket 19 mm | 3.0 mm | DIN 912 / ISO 4762 |
| M30 | 30.0 mm OD | Head OD 45 mm; Hex socket 22 mm | 3.5 mm | DIN 912 / ISO 4762 |
| M36 | 36.0 mm OD | Head OD 54 mm; Hex socket 27 mm | 4.0 mm | DIN 912 / ISO 4762 |
Manufacturing Route at TorqBolt
Socket head cap screw manufacture requires a precision broach for the hex socket and controlled head-underside fillet for fatigue performance:
- Receive Incoloy 800H bar to ASTM B408; PMI verification.
- Cut bar to overall length on bandsaw.
- CNC turn shank and cylindrical head to print OD; face head-end square.
- Broach hex socket to DIN 912 across-flats; controlled socket depth.
- Thread roll the full-length shank: class 6g per ISO 965.
- Solution anneal at 1149 deg C plateau followed by rapid quench; grain size 5 verified.
- Hardness band 120-184 HB; verify hex socket geometry with go / no-go gauge.
- Visual + dimensional + PMI inspection 100 percent; head-mark heat number.
- VCI wrap; pack with optional matched flat washers; CoC + EN 10204 cert.
Socket Head Cap Screw Sizes Stocked and Lead Times
| Diameter range | Length range | Stock status | Lead time |
|---|---|---|---|
| M3 - M8 | 5 mm - 60 mm | Stock + ex-stock | 7 working days |
| M10 - M16 | 10 mm - 100 mm | Made-to-order from stock bar | 10 to 14 working days |
| M20 - M24 | 20 mm - 150 mm | Made-to-order | 14 to 21 working days |
| M30 - M36 | 30 mm - 200 mm | Made-to-order, large bar | 3 to 5 weeks |
Inspection and Heat Marking
Socket head cap screw specific inspections cover the hex socket geometry, head-underside fillet and full-thread engagement:
- Hex socket across-flats verified with go / no-go Allen-key gauge per DIN 912.
- Socket depth verified to ensure full Allen-key engagement.
- Head-underside fillet radius verified per DIN 912 tolerance.
- Full-length thread verified with class 6g ring gauge.
- Hardness band 120-184 HB on first piece and one per batch.
- ASTM E112 grain-size etch verification.
- PMI by X-ray fluorescence on first piece and one per batch.
- Heat number + grade marking on head top.
Typical Service Conditions
Socket head cap screws are specified in restricted-clearance high-temperature assemblies where hex-head wrench access is not available:
- Heat exchanger end-cover and channel-flange bolting in restricted clearance.
- ASME Section VIII pressure-vessel instrument nozzle bolting on narrow pads.
- High-temperature pump and valve assemblies in ethylene cracker service.
- Reformer pigtail bracket fastening in tight access.
- Furnace burner-tile retainer bolting in furnace components.
- Steam superheater support-clip bolting with tight bolt-spacing.
Incoloy 800H Alloy Considerations on This Fastener Form
Companion Fasteners and Related Pages
- Hex Cap Screws: open-clearance hex-head alternative.
- Hex Bolts: partial-thread alternative for through-bolts.
- Stud Bolts: no-head alternative for through-flange bolting.
- Washers: matched flat washers for socket-cap assemblies.
- Hex Nuts: matched nuts when socket cap is through-bolted.
Frequently Asked Questions
Q. Why use socket head instead of hex head?
Socket head cap screw drives with an Allen key from above, requiring no side clearance. Hex-head bolts require a wrench arc and side clearance. Socket head is preferred where instrument enclosures, narrow flange pads or tight bolt-spacing precludes a wrench.
Q. What grade of Allen key is required?
Standard hex socket per DIN 912. Allen key dimensions follow the DIN 911 / ISO 2936 schedule. Hex socket size for each screw diameter is listed in the dimension table above.
Q. Are socket head cap screws available with low-head profile?
Yes on call-out. Standard supply is DIN 912 (cylindrical head). DIN 7984 (low-head socket cap screw) and DIN 6912 (low-head with key guide) are machined to print on PO call-out from the same B408 bar.
Q. What is the maximum diameter supplied?
Standard supply is M3 to M36. M42 and M48 are machined on PO call-out subject to bar availability.
Q. Can socket head cap screws be supplied in inch sizes?
Yes. ANSI / ASME B18.3 socket head cap screws 4-40 through 1-1/2 inch are machined on PO call-out with class 2A UNC threads.
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